Jack Dorsey

No. 392: $1.1 billion

Age: 35

Creator and cofounder of Twitter makes his debut
thanks to Square, the mobile-payment startup
he founded in 2009. The company announced a
partnership with Starbucks in August that will allow
it to process all credit and debit card transactions
for the coffee shop giant. Starbucks also invested
$25 million in Square, valuing it at $3.25 billion.